Hemispherical combustion chamber end dome having cooling air deflecting means



Jall- 1952 w. L. BLATZ 2,581,999

YHEMISPHERICAL COMBUSTION CHAMBER END DOME HAVING COOLING AIR DEFLECTINGMEANS Filed Feb. 1, 1946 Inventor I I Walter L. Blatz by" v His Abtorng.

Patented Jan. 8, 1952 S PATENT OFFICE HEMISPHERICAL COMBUSTION CHAMBEREND DOME HAVING COOLING AIR DE- FLECTING S Walter L. Blatz, Scotia, N.Y., assignor to General Electric Company, a corporation of New YorkApplication February 1, 1946, Serial No. 644,888'

My invention relates to combustion chambers, such as are employed inthermal powerplants. It is particularly applicable to gas turbinepowerplants, for instance those used for the jet propulsion of aircraft.

This invention constitutes an improvement in one component part of thecombustion chamber disclosed in application Serial No. 750,015, filedMay 23, 1947, in the name of Anthony J. Nerad, and assigned to the sameassignee as the present application. Said application is acontinuation-in-part of application Serial No. 501,106, filed September3, 1943, now abandoned. My invention is specifically an improved enddome arrangement for combustion chambers similar to those described inthe above defined applications.

An object of the invention is to provide an improved dome structureforming the closed end 6 Claims. (C1. Gil-39.65) I which Fig. 1 is anassembly view showing in section my improved combustion chamber end domearrangement; Fig. 2 is an. end view in elevation of the dome by itself;and Fig. 3 is a sectional view of the dome taken on the plane 33 in Fig.2.

Referring now to Fig. 1, my invention is disclosed in connection with acombustion chamber indicated generally at I, which is supplied withcombustion air by a transition piece or air adapter 2 from a compressordischarge passage defined by walls 3, which may be part of a centrifugalor axial flow compressor (not shown). A suitable framework indicatedgenerally at 4 forms part of the main frame of the powerplant,supporting a turbine casing 22 in spaced relation to compressor housing3.

"The general arrangement and operation of the combustion chamber l ismore particularly disclosed in the above-mentioned applications ofAnthony J. Nerad. An aircraft gas turbine powerplant having acompressor-combustion chamber-turbine-frame assembly similar to that.partially represented in Fig. 1 is more completely disclosed in anapplication Serial No. 525,391, filed March 7, 1944, in the name of DaleD. Streid, issued December 9, 1947 as Patent No. 2,432,359. It should beunderstood that my invention is equally applicable to other gas turbinepowerplants, for instance those disclosed in applications Serial No.506,930, filed October 20, 1943, now Patent No. 2,479,573, and SerialNo. 541,565, filed June 22, 1944, both in the name of Alan Howard.

The details of the compressor, turbine, and supporting framework are notnecessary to an understanding of the present invention, but it may benoted that the compressor casing 3 is secured by suitable threadedfastenings I to the frame 4, which is in turn secured to the turbinesupport casing 22 by threaded fastenings O.

The combustion chamber l consists of 9. cylindrical liner 1 open at bothends and having a plurality of rows of circumferentially spacedcombustion air inlet openings 8, the nearest row of openings beingaxially spaced from the open end portion 9 of the liner. The arrangementof the air inlet openings is more fully disclosed in the above-mentionedapplications of Anthony J. Nerad. The liner I may be supported at itsdownstream end by various types of suitable supports (not shown), whilethe upstream" end 9 is supported by the dome II in a manner which willappear hereinafter.

Surrounding liner 1 is an outer housing II, which may be supported bysuitable brackets 12 secured to the frame 4 by threaded fastening O. Thehousing ii, like liner I, is circular in cross section, or substantiallyso, and may be supported by an annular member 13 having a flange weldedto the outer housing as indicated at I, and secured to bracket l2 by asuitable threaded fastening 15. The member l3 may also be secured to aballle l6 of flexible material, such as leather, and arranged to engagea cooperating baflle member I! in such a manner as to prevent undesiredcirculation of air around the outside of the combustor housing II. Thisbaflle arrangement may be seen in more detail by reference to theabove-mentioned application of Dale enlarged end of air adapter 2. Thissealed joint comprises a piston ring seal member ll welded permittedsome radial movement in order to take up an eccentric position relativeto member is.

It will be appreciated by those skilled in the art that liner 1 must bemade of very carefully selected metallic alloys able to withstand thehigh temperatures encountered. The outer housing II is not subject tosuch extreme temperatures and may be made of various suitable alloysteels. The piston ring member 18 may be made of stainless steel and therings l9 may be of cast iron. Since air adapter 2 is cast of light metalsuch as aluminum or magnesium alloy,

the end portion 20 may be provided with a bushing 2| of harder materialto provide a bearing surface for the piston rings l9. Bushing 2| may beshrunk or pressed into the air adapter. It should be noted that theouter housing II is rigidly supported in fixed position relative to theturbine casing 22 by the bracket l2 and other suitable means at thedownstream end of. housing ll (not shown).

It will be appreciated by those familiar with gas turbine powerplantsthat housing II is duringoperation heated by radiation from liner 1. toa temperature considerably above that of the frame 4 and compressorhousing 3.

The smallend of air adapter 2 is provided with a transversely extendingflange 23 aligned with an attachment flange 24 on compressor housing 3.The flange 23 issecured to attachment flange 24 by an annular row ofthreaded fastenings. 25 with a cylindrical spacer member 26 insertedtherebetween, for a purpose which will appear hereinafter. It will beobvious that suitable gaskets 21 may be employed, if found necessary toprevent air leakage.

It will be seen from the above that air adapter 2 is rigidly fixed tothe comparatively c001 compressor casing 3, while the heated housing IIis fixed relative to the turbine casing 22. The above described pistonring seal between housing II and air adapter 2 is intended to' permitlimited axial, radial, and angular displacement between the end ofhousing II and the associated end of air adapter 2. By permitting suchdisplacements, assembly of the powerplant is facilitated anddifferential thermal expansion during operation is permitted.

Secured by fastenings 30 to a mounting pad 23 on air adapter 2 is a fuelspray nozzle 29. The nozzle shown is of the duplex type, which is morefully disclosed in an application Serial No. 622,604, filed October. 16,1945, in the names of C. D. Fulton and D. C. Ipsen. The specificstructure of nozzle 29 is disclosed in an application of G. N.Miles,-;Serial Ho. 669,072, filed May 11, 1946, now Patent No.2,524,820, and assigned to the assignee of the present application.However, itshould be understood that the specific type and structure ofthe fuel nozzle used is not essential to an understanding of the presentinvention. It is sufiicient to note that fluid fuel is supplied to thenozzle by conduits 3i and discharged from nozzle tip 32 in the form of asubstantially conical spray pattern indicated by the dotted lines 33.

The, end dome to which my invention specifically relates is shown inassembled relation in Fig. land by itself, to an enlarged scale, in

Figs. 2 and 3. This end dome comprises a thin wall 34, preferably formedfrom suitable temperature-resisting sheet metal, and shapedsubstantially in the form of a hemisphere. Adjacent the pole of thehemisphere is a central opening 60 for receiving the discharge end ortip 32 of the fuel nozzle. The wall around this opening may be providedwith anaxially extending flange 35 dimensioned to slidably engage andsnugly fit the nozzle tip 32. A second flanged opening 36 is provided toreceive the electrode end of a suitable spark-plug 31, shown inassembled relation in Fig. 1. It will be understood that the bushing ofthe spark-plug may be threadedly received in an opening (not shown inthe wall of the air adapter 2.

Circumferentially spaced around the dome, and welded thereto, areradially extending support arms 34a. The tips of these arms are providedwith openings 38. so that the arms can be secured to mounting bosses 39in the air adapter (see Fig. 1) by suitable fastening means such as caprscrews 44. Radially spaced from the central opening 60 is acircumferential row of air inlet openings 40. It will be readilyapparent from Fig; 3 that these openings are formed by making uz-shapedcuts in the dome and deflecting the tongues 4|: so formed inwardly.

Around the rim or equator of the hemispher ical dome is a row ofcircumferentially spaced dimples 42 formed by striking the material of:the dome outwardly in a manner which will be obvious from Fig. 3. Thedimpled outer circumference of the dome-is so dimensioned as to formafree sliding fit with the interior surfaceof liner end portion 9, as maybe readily seen. from Fig. 1. The portions of the circumference of thedome between the dimples 42 define withthe liner end portion 9 aplurality of circum ferentially spaced arcuate slots 43. r

The method of assembly of my improved com-: bustion chamber dome is asfollows. Thefuel, nozzle 29 is assembled to the air adapter .2 throughthe opening defined by mounting pad; 28. The dome I 0 is then assembledwith the" central flange 35 slipping over the nozzle tip 32, and thearms 34a are secured to bosses .39 by the threaded fastenings 44. .Then,assuming. that the liner land housing II, compressor-.- housing 3,framework 4, and turbine casing 22 have been previously assembled, theair adapter is moved transversely into position in the space" betweenthe piston ring assembly [8, 19, and the compressor discharge casing 3.The'"'axial length of the spacer 26 is so selected that sum cient spaceis provided to permit ready in-' sertion of the air adapter in thismanner (when spacer 26 is removed). Once the end portion- 20 of the airadapter is slid over the piston rings l9 it will be obvious that airadapter 2 can be moved axially with respect to the combustion chamber I,the dimpled circumference of dome l0 sliding into the open end 9 ofliner 1, until suflicient clearancev is provided at the other end of theair adapter to insert spacer 26" transversely into the position shown inFig. 'l.f To remove the air adapter for inspection and .1 servicing ofthe fuel nozzle and the end dome, the i above procedure is followed in.reverse; that is," screws 25 and spacer 26 are removed, and the airadapter 20 is moved axially with respect to. the. combustion chamber Iuntil end portion 20 disengages from the piston rings IS, thecircumfernc d m a wh b wi rawn.

sembly and disassembly to rotate air adapter 2 (after removing spacer26) about an axis parallel to the axis of the' combustion chamber, suchrotation causing the end flange 23 to move radially outward so as toeasily clear the attachment pad 24 on compressor casing 3. l

It will be-observed'that the brackets l2, as well as the air baflie l6,are secured to the outer housing H by means which are independent of thepiston ring sealed slip-joint l8, I9, 20. Thus the air adapter 2,complete with fuel nozzle 29 and dome It can be inserted and removedfrom the powerplant simply .by removing the spacer 26, and withoutdisturbing other parts of the combustion chamber and associated parts.This con-I siderably facilitates maintenance of the powerplant becauseof the frequency with which the air adapter must be removed forservicing the nozzle and dome and for cleaning, repairing or replacingthe liner 1.

" Besides lending ease of assembly and disassembly, the piston ringsealed slip-joint l8, I9, 20 has the additional advantage of providingthe flexibility needed for permitting differential thermal expansion andcompensation for misalignment.

Referring now to Fig. 1, the operation of the apparatus is as follows.Air from the compressor discharge casing 3 flows in the direction of thearrows into the annular space defined between liner I and housing I I.From this space it flows through the combustion air inlet openings 8 inthe manner indicated by the arrows 46, as more specifically described inthe above-mentioned applications of Anthony J. Nerad. Some air alsoflows along the inner surface of liner 1 through the arcuate slots 41formed between dimples 42, This flow is in the direction of the arrow 41in Fig. 1' and forms a thin sheet of pure comparatively cool air so asto insulate" the inner surface of liner 1 from contact with hot productsof combustion containing unburned fuel particles. If such particles werepermitted to contact the comparatively cool surface of liner 1, theywould be deposited in the form of unburned carbon. Thus, it will be seenthat the air flow 41 serves both to cool liner 1 and to insulate it fromcontact with unburned carbon particles which might otherwise bedeposited thereon.

Air also flows as represented by arrows 48 It has been found by muchtesting and actual. operating experience, that combustion chambers ofthe type desired in the above-mentioned Nerad applications embodying myimproved dome with the construction described herein have a number ofimportant advantages. The dome and nozzle tip are kept within safetemperature limits and free of carbon deposits. Also, the flame in thecombustion chamber appears to be more stable over a wide range ofdiflicult operating conditions. While it is not definitely known, Ibelieve this to be due to the fact that the reversely flowing coolingand insulating air 49 forms what might be considered an elasticboundary" for the combustion tore 50, 5|. It is believed that as theoperating conditions vary, the thickness of the insulating layer 49changes somewhat with a corresponding change. in the volume occupied bythe combustion tore 50, 5|. This appears to have a beneficial effect onthe combustion process.

It will be understood by those skilled in this art that the liner 1 andthe end dome ID are most subject to deterioration during the operationof the powerplant and therefore require most frequent inspection,servicing, and replacement. It will be seen that my invention provides asimple end dome which is easy and cheap to fabricate and can be readilyserviced when in need of cleaning, repair or replacement. Theconvenience of disassembling the arrangement facilitates frequentinspection and servicing and thus lengthens the time interval betweenmajor powerplant overhauls.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. An end dome for a, combustion chamber of the type having anopen-ended liner comprising a; wall defining a substantiallyhemispherical surface having a central opening arranged to receive fuelinjecting means adjacent the pole of the dome and having acircumferential row of openings, deflector means including a wallportion spaced from said wall in cooperative relation with each of saidopenings to form a plurality of nozzles facing said central opening fordirecting through the slots 40 formed by the inwardly struck tongues 4|.Slots 4!) form. nozzles which direct a comparatively thin sheet ofcooling and insulating air inwardly toward the nozzle tip 32 in thedirection of arrows 49. This cooling and insulating air flows over theexposed end surfaces of nozzle tip 32, thereby also keeping them freefrom carbon deposits. It will be apparent from the arrows in Fig. 1 thatthis cooling and insulatingair after passing over nozzle tip 32 flowsreverselyin the same direction as the combustion air flow represented byarrows 50. The combined flow of primary combustion air 50 and coolingand insulating air 49 then flows axially through liner 1, some of itrecirculating in the manner indicated by arrows 5| to form the toroidalflow path or "tore more specifically described in the above-mentionedapplications of Anthony J. Nerad. The portion of the combined air flow49, 50 which does not recirculate in the manner of arrows 5| flowsaxially down the liner 1 passing between the circumferentially spacedradial jets 46 of inflowing combustion air.

a comparatively thin sheet of cooling and insulating air over the innersurface of the dome inwardly toward said central opening.

2. In a combustion chamber for a thermal powerplant the combination of afirst wall defining an open ended liner of substantially circular crosssection, an outer housing surrounding said liner, a dome adapted to forma closed end wall of the liner, and means supporting the dome from saidhousing, the dome comprising a wall defining a substantiallyhemispherical surface with a central opening located adjacent the poleof the dome, fuel injecting means supported in said housing and having adischarge end cooperatively associated with said central opening, saiddome also having openings therethrough radially spaced from said centralopening and arranged to direct a comparatively thin sheet of cooling andinsulating air over the inner surface of the dome inwardly toward thecentral opening, the outer circumference of said dome havingcircumferentially spaced projections arranged to engage the innersurface of the adjacent end of said liner so as to define therewithcircumferentially spaced arcuate slots arranged to direct a thin sheetof cooling and insulating air axially along the inner surface of saidliner toward the open end thereof.

3. An end dome for an open-ended combustion chamber liner comprising awall defining a-substantially hemispherical inner surface and hav-' ofsaid'openings to form a plurality of nozzlesfacing said central openingfor directing a comparatively thin sheet of air over the inner surfaceof the dome radially inwardly toward said central opening.

4. An end dome for an open-ended combus tion chamber liner comprising awall defining a substantially hemispherical inner surface and having acentral portion defining an openingadapted to receive the discharge endof fuel injecting means, said wall also defining a plurality. ofopenings radially spaced from the central-opening and arranged to directa comparatively thin sheet of air over the inner surface of the, domera.-. dially inwardly toward said central opening, and a plurality ofprojections spaced around the outer circumference of the dome andarranged to engage the inner surface of the liner to define therewith aplurality of circumferentially spaced arcuate slots. 1

5. An end dome for a cylindrical combustion chamber liner comprising athin wall defining a substantially hemispherical surface and having acentral opening adapted to receive fuel injection means, the rim portionof said wall forming circumferentially spaced projections adapted002811- gage the inner surface of the liner, and other'portions of thewall intermediate said central opening and said rim portion definingnozzles adapted todirect cooling and insulating air in a thin sheetalong the inner surface of tlie dome radially inwardly toward saidcentral opening.

6. An end dome for a cylindrical combustion 8 chamber liner comprising athin-wall defining a substantially hemispherical surface a centralopening surrounded by an arcially ex"- tending flange adapted toslida'b'ly'f engage the outer circumferential surface 01' fuel injectionnozzle means, the rim portion'of said wall forming circumferentiallyspaced projections adapted to engage the inner surface of the liner,andother portions of the wall intermediate saidcentral opening and saidrim portion'deflning nozzles adaptedto direct cooling and insulating airin a thin sheet-along the inner surface of the-dome radially inwardlytoward sald'central opening. WALTER L. BLA'IZ.

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